Electric friction brake



A. P. WARNER ELECTRIC FRICTION BRAKE Filed Feb. 17, 1950 Z1/rafael".

June 7, 1932.

Patented June 7, 1932 UNITED STATES PATENT OFFICE .ARTHUR P. WARNER, 0F BLOIT, WISCONSm, .ASSIGNOR TC WARNER ELECTRIC BRAKE CORPORATION, OF SOUTH BELOIT, ILLINOIS, A CORPORATION 01E' ILLINOIS ELECTRIC marion nnaxn Application filed February 17, 193D. Serial No. 428,904.

energizing winding. The eHi'ciency of mag nets of this character are extremely powerfnl in their action when there is practically no air gap between the coacting portions of the magnet and its armature.- But in the environment vabove described, the inherent lateral wobbling of the vehicle Wheel, due to the allowable looseness of the parts and other causes, tends to produce an air gap of such relatively large width as to render a brake of y the above character practically uncontrollable. That is to say, a current applied to the brake magnet of an intensity suilici'ent to overcome the gap between the magnetic elements will, when the elements are brought into mechanical Contact and the gap thereby eliminated, produce a severe and excessive braking action. Thus, it is impossible .to obtain the sensitive control and graduated application of the brake which is required in order to render such a brake suitable for use on modern automotive Ivehicles.

It is the object of the present invention to overcome the objection above mentioned through the provision of a novel supplementalV means which acts independently of the main brake magnet to urge the normally separated magnetic' elements into mechanical contact and thereby efl'ectually overcome any air gap between the elements.

Another object is to place the supplemental means 'above referred to under the controlof the same means that controls the energization of the brake so that any, air'gap between the magnetic elements will be overcome automatically.

Othcr objects and advantages of the invention will become apparent from thefollowing detailed description taken in connection with the accompanying drawing, in 'which Figure 1 is a fragmentary view in vertical section of a vehicle wheel equipped with a brake embodying the features of the present invention, the section being taken substantially along the line 1 1 of Fig. 2.

Fig. 2 is a fragmentary sectional view taken along the line 2 2 of Fig. 1.

Fig. 3 is an enlarged view of the upper portion of Fig. 1.

Fig. 4 is a wiring diagram of the brake conJ trol circuits.

While the invention is susceptible of various modiications and alternative constructions, I have shown in the drawing and will herein describe in detail V-the preferred en1- bodiment, but it is to'be understood that I do not thereby intend to limit the inventionV to the specific form disclosed but intend to cover all modifications and alternative constructions falling within the spirit and scope of the invention as expressed vin the appended claims.A

In the exemplary formshown in the drawing, the invention is embodied in an electric brake including a rotatable drum 6 having the usual flange bolted or otherwise secured to the inner end of a. hub 8 of a vehicle wheel 9. The inwardly opening end of the drum is closed by an annular plate 11 suitably secured to a steering knucklef12 or other relatively non-rotatable part.`

the present instance, the non-rotatable friction surface of the brake is of the band type comprising a metal strip 13 encircling.

aninwardly projecting iange 14 on thefan- Chor plate and carrying segments 15 of fric, tion material. Fittings 16 are secured to the opposite ends of the strip 13 and drawn by a spring 1'( into abutting `engagement with the opposite end surfaces of astop 18 rigid with the anchor plate.

The operator for spreading the ends of the band apart, thereby setting the brake, comprises two riugs 19 and 20 of magnetic material arranged concentric with the drum and adapted for axial gripping engagement/` The ring 19, which constitutes the magnetic armature, is of rectangular cross-sectional shape 10u and relatively narrow axial width. Preferabl this ring is of solid metal construction an `iioatingly supported from the drum so as to rotate therewlth, at the same time being adapted Ifor some degree of axial movement. To this'end the back of the ring is secured at annularly spaced points to the ends of fiexible'metal strips 21 which extend in a adirection substantially tangent to the' ring 19, and

` m are rigid at their other ends with a rin 22 in turn riveted to the drum flange 7. en the wheel and drum with the larmature unit A mo'unted thereon are placed on the axle, the

inwardly facing frict1on face of the armature is' urged away from thevdrum ange 7 bg' springs 24 acting in compression between-A t e rings 19'and 22. This inward axial move-- ment of the-armature is limited by engagement ofarms .on the armature and stop A surfaces 23 on the ring 22.- The strips 21, 1t

will be observed, act in tension` to prevent relative rotation between the rings 19 and 22 in one direction. RelativeI rotation in the other 'direction is prevented by engagement g5 between the ring 22 and the arms 25.

The ring 22 constitutes the magnet proper and is U-shaped in cross-section with a windmg 26 disposed between its two concentric poles 27, which are separated by plates 28 of 0 non-magnetic material providing a wear resisting surface substantially flush lwith the end faces of the poles and adapted to sustain, the axial pressure between the two magnetic rings. The magnet is supported by a circas lar flange portion\29 of the anchor cplate for oscillation about the drum axis and for axialmovement toward and away fromthe face of the armature ring.` Normally, that is when the magnet is deenergized, the magnet is drawn away from the armature by springs 30 actingA in tension between the magnet and the anchorplate. Thus'the faces ofjthe magnet' and armature are separated by an air gap of such width that the faces do not come into mechanical contact due to the lateral wobblingzof the armature in the rotation of the vehicle wheel.` Projecting rigidly from the outer magnet y pole are two actuating lugs 31 having oppo- ,sitely facing surfaces positioned to abut vagainst lu s 32.which are rigid .with the lit-- tings 16. pon movement of the magnet in either direction away froml normal brakereleased position (Fig. 2), one orthe other ofthe lugs 31'wil1 move its end of the brake ^away'from thestop 18, thereby expanding the band and pressing its entire friction surface against the drum. The lugs 31, it will be observed, do not hinder the axial movea0 ment of the magnet ring.

y The magnet windings"26 for the-different brakes ofthe vehicle 'are arranged t'o be energized from. the storage battery 33 by manipulation of a rheostat 34 (Fig. 4) by 95 the vehicle driver. The rheostat shown herein diagrammatically comprises'. a plurality of resistance elements 35 connected to a commdn conductor 36 whichleads to one terminal end of each winding 26. The other ends l of the winding are ounded to the-vehicle frame. At their ot er ends the resistance elements 35 are connectedv to resilient metal strips 37 whose ends are arranged to be engaged successivelyby a contact plate 38 on a lever A39 pivoted at 40 and adapted' to be moved into abutment witli the strips37'b'y' actuation of a foot pedal or other controller (not shown) within the reach of the vehicle driver.

Thenonunded terminal of the storage ,battery 33 1s connected to a strip 41 of the rheostat which is normally engaged bythe contact plate 38 when the controller is in inactive position. Thus, when the controller pedal is depressed suiliciently to bring the contact plate against the first resistance strip 37, the circuit through the windings 26 will be completed.. Further movement of the controller will increase the intensity of the current by cutting in additional resistance elements successively. l v s The current which is caused .to flow through the windings 26 upon the initial closure of the circuits by the rheostat 34 is 'of such a small magnitude as to be incapable of overcoming the air ap normally interrupting the magnetic" ux circuit through the magnet and armature rings. Means is therefore provided which acts independently ofV the brake magnet to bring the two rings into mechanical contact substantially coincident with the a plication of current to the winding 26.- his means comprises a supplemental magnet whose action is not materially affected by variations in the position of its armature relative to the magnet core. The supplemental magnets herein employed are of the solenoid type, each comprising a tubular coil 42 4(Fig. 3) mounted in a core 43 which is located externally of the anchor plate 11 substantially opposite the magnet ring 20.- The armature o -each solenoid 1s inv the form of :LT-shaped plunger 44, -whose shank is slidable endwise .in a central aperture ofthe ,core 43 and is adaptedto apply an actuating force tothe magnetring 20 through the medium f a rod 45 which pro- ]'ects through the anchor plate and a backing pad 46 and bears against the back of the magnet ring.` Thus, when the solenoid is energized, the magnet ring is moved against the contact with the friction surface of the latter,

thereby closing the air gap between' the rings witha resultant reduction in the reluctance in the magnetic circuit through the Each solenoidv an its armature may be suitably enclosed in a 4cup-shaped casi'ng 47 secured to theouter sideof the anchor plate.

y the current application to and regulates the Y the armature is current flow in the main winding. This means comprises the foot pedal controller of the rheostat and in order that the current for` the solenoids may be of different intensityA than that in the winding 26, it is preferred to interposethe solenoid coils 42 in circuits independent ofthe main windings 26. For this purpose one terminal of` each coil 42 is grounded to the vehicle frame and the other is connected by an insulated cable conductor 48 to a' metal strip 49 incorporated in the rheostat so that its free end will be engagedby the contact plate 38 prior to or substantially simultaneously with the engagement of the first resistant strip 37. Thus, the strips 41 and 49 and the contact plate form a switch which is closed to complete the energizing circuit for the solenoids as an incident to the application of current to the main brake windings.

The brake above described operates in the following manner when the vehicle driver depresses the foot pedal controller. .Upon

engagement of thecontactplate 38 with the strip 49, all of the'V solenoid coils 42 will be energized causing their plungers 44 to move inwardly and force the magnet against the action ofthe springs 30 into mechanical contact with the face of the armature ring 19, thereby closing the magnetic. circuit through the two rings. No appreciable gripping action takes place at this time between the-magnet and armature rings owing to the'fact that yieldable in an axial direction.

lilngagementA between the contactor and the first resistance strip 37 applies current to the winding 26 causing gripping engagement between the friction surfaces of Y the two rings proportional to the strength of the energ1zing current, whereupon the mag-A net ring willbe driven frictionally by the armature ring, thereby moving with the wheel a short angular distance.- In this' movement one end of the band s moved away from the stop 18 whichv expands the band, thereby pressing the segments 15' against-the drum surface. After the normal clearance has been taken up angular movement of the magnet ceases, causing slippage between the ring surfaces inthe continued rotation ofthe wheel.

Further movement of the rheostat controller increases the gripping action between the rings 19 and 20 and therefore varies the retarding action applied to the vehicle wheels. When the rheostat controller is returned to normal position (Fig. 4), the current flow through the windin s 26 and the solenoid coils 42 is interrupted, whereupon the spring 17 then acts through the medium of the fitting 16 and the lug 31 to restore the magnet as well as the actuated end of the band to normal position. At the same time, the rings 19 and 20 become separated under the action ofvl the springs 30.

N o claim is made herein to the mannerof mounting the magnet and armature, the manner of transmitting the movement of l the magnet tothe friction band, the construction of the anchor plate, and of the controlrheostat, such features forming the subject matter of my co-pending application Serial No. 428,905, filed February 1 7,` 1930, and of John Whyte, Serial No. 280,173, filed May 24, 1928,

Serial No. 417,385, filed December 30, 1929, and Serial No. 428,870, filed Februar 17, 1930, and a copending application of wan Leveen, Serial N o. 393,380, filed September 18,1929.

I claim as my invention:

1.l In an electric vehicle brake, the combination of 'a drum rotatable with a Wheel of the vehicle, a non-rotatable plate closing the open end of said drum, a pair of annular magnetic rings arranged for axial gripping engagement to determine vth'e degree of braking action applied to said wheel, one of said elements being rotatable with said drum,

.Serial No. 320,129, led November 17 1928,

the other being mounted on said plate for ioating axial movement relative to said plate, Aa magnet winding carried by one of 'said elements and adapted when energized to produce gripping engagement between the coacting surfaces ofthe elements, spring means acting on said last mentioned element and normally holding the same out of mecham'call contact `with said other element, a solenoid magnet mounted exterlorly of said plate and having an armature plunger movable in a direction parallel to the drum axis, said plunger, upon energization of said solenoid, being projected against said last mentioned magnetic element and acting tomove the same into mechanical contact With the'y rotatable element, and manually operable means'for applying energizing current to said winding and said solenoid. f

2. An electric friction brake having, `in combination, a magnetic element having an annularv friction surface which rotates dursaid elements in a posing element thereb causing ppm 'engagement of said friction surdlces, ygieldable means normally acting to hold' said Africtfon -surfaces' out of contactwhile said winding is deenergized, manually controllable means for applying an energizing current of variable intensity to said winding, and means supplemental to said'windlng and acting automatically as an incident to the operation of said manually controllable 'means to overcome the action of said yieldable means and thereby bring said surfaces into mechanical contact independently of said winding.

3'. In an electric friction brake for a vehicle, a pair of-rings of magnetic-.material having opposed annular faces, one Aof said rings being rotatable during motionV of the vehicle, a winding carried by one of said rings and adapted when energized to create a magnetic fini which threads the ferromagnetic circuit through the-faces of said rings thereby causing frictional gripping engagement the magnitude of which determines the degree of braking action, control means governing the closure. of an energizin circuit through said winding, the faces o? rings bein maintained out of mechanical contact while said winding is deenergized, a supplemental electromagnet adapted when energized to urge said rings into mechanical contact, and a single manually .operable controller for governing the energization of said winding and said electromagnet.'

4. In an electrically controlled friction the combination of two annular mag. \netic elements having friction faces arranged brake,

for axial pping engagement, one of said selements being rotatable with the part to be braked, a magnetic winding carried' by one of said elements and adapted to control the degree of gripping engagement between the elements, means normally acting to maintain said faces out of frictional contact, a supplemental felectromagnet adapted when ener-- actuating force to one of direction to bring the friction faces into mechanical contact, and a gizedV to apply an said winding and said electromagnet may be energized and the intensity of the energizing current in said winding varied to produce varying degrees of braking.

5. In an electrically controlled friction brake, the combination of two annular magnetic elements having friction faces arranged for axial 'pping engagement, one of said elements being rotatable with the part to be Abralred, a magnetic winding carried by one of said elements and adapted Ato control the degree of gripping engagement between the elements, means normally acting to maintain said faces out of frictional contact, a supple- -mental electromagnet adapted when enersaid gized to apply Aan actuating force to one of said elements in a direction to bring the friction faces into mechanical contact, a rheostat. controlling the application of current to and the intensity of t e current flowing in said winding, a switch controlling the application of current to said electromagnet, and a common actuating/ means for said switch and rheostat operable to apply current to said winding and electromagnet substantially simultaneously and in continued movement toincrease the intensity of the current energizing said winding. l y i 6. In an electrically controlled friction brake, the combination of two annular magnetic elements having friction faces arranged forI axial. gripping engagement, one of said elements being rotatable with the part to be brakeda magnetic'winding carried by one of said elements and adapted to control the degree of gripping engagement between the elements, means normally acting to maintain said faces out of frictional contact, a solenoid magnet having an armature operatively associated with one of said elements and adapted when energized to ap ly a force toone side of the element in a 'rection to move that element into mechanical contact with the other element, and manually controllable means for governing the application of energizing current to said winding and solenoid.

7. In an electrically controlled friction brake, the combination of two annular magnetic elements having friction faces arranged for axial gripping engagement, one of said elementsv being rotatable with the part to be braked, a magnetic winding carried by one of said elements and adaptedto control the degree of gripping engagement between the elements, said elements being normally maintained vout of mechanical contactwith each other, means for applying energizing current to and controllably varying the current in said winding to effect varying degrees of braking action, and means actin substantially coincident with the application of current to said winding to establish mechanical contact-between said elements independently of the attractive force produced by said win single manually operable controller by which ing 8.. In an electrically controlled friction gree of gripping engagement between the elements, spring'means normally acting' to separate said elements and maintain their brake, the combination of two annular magfriction faces out of mechanical contact, an

electromagnet of the solenoid type having an armature plunger operatively associated withy one of said elements and movable, upon eifergization of the solenoid, in a direction to bring said friction faces into mechanical contact against the action of said s ring means,

and means operable automatical y in the application of energizing current to said windin dto apply energizing current to said soleno1 e 9. In a brakingsystem for an automotive vehicle, the combination of a brake having two annular magnetic elements arranged for axial gripping engagement and normally maintained out of mechanical contact, a magnetic winding adapted to be variably energized to control the degree of gripplng en gagernent between said elements and therefore the braking action on the vehicle, and means controllable by the vehicle driver and operable to produce mechanical contact between said elements substantially coincident with the application of current to said winding so that the latter need not overcome the air gap. normally maintained between said elements.

l0.v In a braking system foran automotive vehicle, the combination of a brake having two annular magnetic elements arranged for axial gripping engagement and normally maintained out of mechanical contact, a magnetic winding adapted to be variably energized to control the degree of grippino' engagement between said elements and t erefore the braking action on the vehicle, a device. controllable by the vehicle driver and operable upon movement in one direction to apply an energizing current to said winding and then to increase said -current progressively, and means supplemental to said winding-rendered active by operation of said device and operable to produce mechanical contact between saidy elements substantially simultaneously with the initial current application to said winding. p

In testimony whereof, I- have hereunto affixed my signature. l

ARTHUR P. WARNER. 

